The invention relates generally to continuous casting.
More particularly, the invention relates to an arrangement for stirring the molten core of a continuously cast strand in a continuous casting apparatus.
It is known to stir the molten core of a continuously cast strand during a continuous casting procedure. Stirring is accomplished by means of electromagnetic forces either in the mold or along the secondary cooling zone.
For billets and blooms, the stirrer is often incorporated in the mold. The electromagnetic field must here penetrate the mold wall which, as a rule, consists of copper. The magnetic field must further penetrate a gap for cooling water as well as the walls defining the gap and the walls of the stirrer housing. This results in a high consumption of electricity and correspondingly high operating costs.
The West German Patent No. 29 11 187 discloses a continuous casting mold which is constructed as a composite body and consists of an upper mold portion and a lower mold portion. The upper mold portion has copper walls while the lower mold portion has walls of antimagnetic material and is provided with stirring coils. Since the casting passage in this mold is defined by two different metals, problems can occur at the joint between the upper and lower mold portions due to the different coefficients of expansion. Gaps can be created at the joint and warping can take place thereby generating difficulties in starting, defects in the strand and breakouts.
The West German Patent No. 27 31 238 discloses a mold which is equipped with a stirrer at the end of the casting passage. The stirrer is screwed to the bottom of the mold and the length of the stirrer can be changed depending upon the requirements. The plurality of stirrers in and below the mold causes the consumption of electricity to be high. Moreover, the stirrers must necessarily be demounted with the mold during each mold change. In addition, new molds and, as a rule, new mold tables as well, are required when installing stirrers in existing continuous casting apparatus which previously did not have stirrers.